1. Field of the Invention
This invention relates to a complex magnetic head, which is provided in a flexible disk drive (FDD) used in, for example, a computer, a personal computer and a portable information terminal device and is used to perform the magnetic recording of information onto a magnetic recording medium such as a magnetic disk or the magnetic reproduction of information therefrom, and to a method of manufacturing the complex magnetic head.
2. Description of the Related Art
Generally, the dominating FDDs are those which are ready for a 3.5-inch-diameter magnetic floppy disk (FD). Nevertheless, the storage capacity thereof has been 2 MB for many years. However, recently, the storage capacity required for image recording, graphic processing and speech processing of one file of data has exceeded 2 MB. Therefore, large capacity FDDs are needed. However, in view vast amount of date stored to the present on 2 MB FDs, such large capacity FDDs should be able to use 2 MB disk media (namely, should be compatible with lower rank or order FD's).
An example of such an FDD is the 120 MB FDD disclosed in "Shin-Gaku-Giho MR95-68" (published by the Institute of Electronics, Information and Communication Engineers of Japan in 1995). In the case of the multi-gap (magnetic) head of this 120 MB FDD, a 120 MB use core, whose track width is 8 .mu.m, and a lower rank read/write (HD) use core, whose track width is 125 .mu.m, are embedded in a U-shaped ceramic slider and are fixed by using fused glass.
Referring next to FIG. 23, there is shown a perspective view of a conventional complex magnetic head disclosed in, for instance, Japanese Laid-open Patent Publication No.3-263602. As shown in this figure, a lower rank core assembly 3, a higher rank core assembly 4 having a higher recording density than that of the lower rank core assembly 3, and a spacer plate interposed between these core assemblies 3 and 4 are placed between a pair of sliders 1 and 2. Further, a coil 6 is placed inside the sliders 1 and 2. Moreover, back cores 8 and 9 are connected to the edge portions of the core assemblies 3 and 4, which are opposite to a disk sliding surface.
Next, a method of manufacturing the upper rank core assembly 4 of FIG. 23 will be described hereinbelow. First, as shown in FIG. 24, a magnetic material base 11 made of a high permeability magnetic material such as ferrite is joined by a cementing material 13 to a nonmagnetic material board 12 made of a nonmagnetic material such as a ceramic or a nonmagnetic ferrite. Subsequently, as shown in FIG. 25, a plurality of track grooves 11a are formed in a surface portion of the magnetic material base 11. Moreover, a winding groove 11b is formed in the magnetic material base 11 in such a manner as to extend perpendicular to the track grooves 11a.
Meanwhile, as illustrated in FIG. 27, a magnetic material base 14 and a nonmagnetic material base 15, which are different in thickness from the corresponding magnetic material base and the corresponding nonmagnetic material base shown in FIG. 24, respectively, are joined together by a joining material 16. Further, as illustrated in FIG. 28, track grooves 14a are provided in a surface portion of the magnetic material base 14. Thereafter, thin films made of high saturation magnetic flux density materials such as Fe-Al-Si alloys are formed on the L-core block of FIG. 26 and the I-core block of FIG. 28, respectively, as needed, by performing a sputtering process or a vapor deposition process. Then, thin films made of SiO.sub.2 and CrO.sub.2 are provided so as to form a recording and reproducing gap. Subsequently, as illustrated in FIG. 29, the core blocks are butted in such a way as to align the track grooves of one of the core blocks with the corresponding track grooves of the other core block, respectively, and are joined together by a joining material 17, whose melting point is lower than those of the joining materials 13 and 16.
The resultant core block obtained by joining the L-core block with the I-core block in this way is then cut along cutting lines 18 and 19 in such a manner as to have a shape as illustrated in FIG. 30. Moreover, the resultant core block is further cut along a cutting line 20 of FIG. 30 and finally undergoes lapping. Thus the upper rank core assembly 4 as illustrated in FIG. 31 is obtained.
In the case of the complex magnetic head as shown in FIG. 23, portions (indicated by reference numerals 12 and 15 in FIG. 31), which are unnecessary for forming magnetic circuits of the core assemblies 3 and 4, are made of nonmagnetic materials. Thereby, the crosstalk induced between the core assemblies 3 and 4 is reduced. Further, the presence of the nonmagnetic material portions 12 and 15 prevents the magnetic head from being damaged when a magnetic disk makes contact with the disk sliding surface 7.
Further, FIG. 32 is a perspective diagram illustrating a conventional complex magnetic head as disclosed in Japanese Laid-open Patent Publication No. 63-103408. Lower rank core assembly 24 and upper rank core assembly 25, which are different in gap length or core width from each other, are placed between a first slider 21 and a second slider 22 and between the second slider 22 and a third slider 23, respectively. Further, a groove 22a is provided in the surface portion of the second slider 22 placed between these core assemblies 24 and 25.
Thus, the core assemblies 24 and 25 are placed separately from each other across the groove 22a formed in the sliding surface portion of the second slider 22. Thereby, magnetic interference is prevented from being caused between the core assemblies 24 and 25.
In the case of the conventional complex magnetic head configured as described above, there is the necessity of assembling the lower rank core assemblies 3 and 24 and the upper rank core assemblies 4 and 25 by precisely positioning these assemblies after the lower rank core assemblies 3 and 24 are manufactured separately from the upper rank core assemblies 4 and 25. Thus, assembly facilities and jigs are costly, and assembly time is long.
Further, in the case of the complex magnetic head illustrated in FIG. 23, the magnetic gap is formed after the magnetic material bases 11 and 14 are joined to the nonmagnetic material bases 12 and 15, respectively. Thus, there is the possibility that a warpage or deformation occurs in the core blocks. Consequently, the uniformity of the gap length is degraded. Moreover, in the case of the complex magnetic head illustrated in FIG. 32, the core assemblies 24 and 25 are arranged to span the whole slider, so the inductance thereof is high. In response to this, especially, in the case of the upper rank core assembly 25 whose recording density is high, the impedance thereof is high owing to this increase in inductance. Consequently, the electromagnetic conversion performance of the magnetic head is degraded.